Oh, don't beat yourself up - you did just great with Milu!!! Scales are so very different - and just like humans, a dog's weight can vary too - throughout the day, or from day to day.
How is she doing now? It would be normal for her to be very, very sleepy/groggy tonight - so that's normal; that's just the anesthesia. Do try to give her some water, and some Nutrical is just fine. If she wants to eat, that's fine too.
Hopefully, they sent you home with pain meds - and be SURE to use them for her, as they directed. Definietly use them, as she will heal better if she is not hurting/stressed. She will perk up some time tomorrow.
